1. Introduction

This is a Maven plugin for managing Docker images and containers. It focuses on two major aspects for a Docker build integration:

1.1. Building Images

One purpose of this plugin is to create Docker images holding the actual application. This is done with the docker:build goal. It is easy to include build artefacts and their dependencies into an image.

Several ways for configuring the builds are supported:

An own configuration syntax can be used to create a Dockerfile. For specifying artefacts and other files, the plugin uses the assembly descriptor format from the maven-assembly-plugin to copy over those file into the Docker image.

An external Dockerfile can be specified in which Maven properties can be inserted. This is also the default mode, if only a single image should be built and a top-level Dockerfile exists. See Simple Dockerfile build for details of this zero XML configuration mode.

Images that are built with this plugin can be pushed to public or private Docker registries with docker:push.

1.2. Running Containers

With this plugin it is possible to run completely isolated integration tests so you don’t need to take care of shared resources. Ports can be mapped dynamically and made available as Maven properties to your integration test code.

Multiple containers can be managed at once, which can be linked together or share data via volumes. Containers are created and started with the docker:start goal and stopped and destroyed with the docker:stop goal. For integration tests both goals are typically bound to the the pre-integration-test and post-integration-test phase, respectively. It is recommended to use the maven-failsafe-plugin for integration testing in order to stop the docker container even when the tests fail.

For proper isolation, container exposed ports can be dynamically and flexibly mapped to local host ports. It is easy to specify a Maven property which will be filled in with a dynamically assigned port after a container has been started. This can then be used as parameter for integration tests to connect to the application.

1.3. Configuration

The plugin configuration contains a global part and a list of image-specific configuration within a <images> list, where each image is defined within a <image> tag. See below for an example.

The global part contains configuration applicable to all images like the Docker URL or the path to the SSL certificates for communication with the Docker Host.

A <run> configuration describing how containers should be created and started.

The <build> and <run> parts are optional and can be omitted.

1.4. Example

In the following examples, two images are specified. One is the official PostgreSQL 9 image from Docker Hub, which internally is referenced with an alias "database". It only has a <run> section which declares that the startup should wait until the given text pattern is matched in the log output. Next is a "service" image, which has a <build> section. It creates an image which has artifacts and dependencies in the /maven directory (and which are specified with an assembly descriptor). Additionally, it specifies the startup command for the container, which in this example fires up a microservice from a jar file copied over via the assembly descriptor. It also exposes port 8080. In the <run> section this port is mapped to a dynamically chosen port and then assigned to the Maven property ${tomcat.port}. This property could be used, for example, by an integration test to access this microservice. An important part is the <links> section which indicates that the image with the alias of "database" is linked into the "service" container, which can access the internal ports in the usual Docker way (via environment variables prefixed with DB_).

Images can be specified in any order and the plugin will take care of the proper startup order (and will bail out if it detects circular dependencies).

Example plugin configuration

<configuration><images><image><alias>service</alias>(1)<name>fabric8/docker-demo:${project.version}</name><build>(2)<from>java:8</from>(3)<assembly><descriptor>docker-assembly.xml</descriptor>(4)</assembly><cmd>(5)<shell>java -jar /maven/service.jar</shell></cmd></build><run>(6)<ports>(7)<port>tomcat.port:8080</port></ports><wait>(8)<http><url>http://localhost:${tomcat.port}/access</url></http><time>10000</time></wait><links>(9)<link>database:db</link></links></run></image><image><alias>database</alias>(10)<name>postgres:9</name><run><wait>(11)<log>database system is ready to accept connections</log><time>20000</time></wait></run></image></images></configuration>

1

Image configuration for a Java service with alias "service" and name fabric8/docker-demo:${project.version}

Support for Docker daemons accepting http or https request via TCP and for Unix sockets

2. Installation

This plugin is available from Maven central and can be connected to
pre- and post-integration phase as seen below. The configuration and
available goals are described below.

Example

<plugin><groupId>io.fabric8</groupId><artifactId>docker-maven-plugin</artifactId><version>0.26.0</version><configuration>
....
<images><!-- A single's image configuration --><image>
....
</image>
....
</images></configuration><!-- Connect start/stop to pre- and
post-integration-test phase, respectively if you want to start
your docker containers during integration tests --><executions><execution><id>start</id><phase>pre-integration-test</phase><goals><!-- "build" should be used to create the images with the
artifact --><goal>build</goal><goal>start</goal></goals></execution><execution><id>stop</id><phase>post-integration-test</phase><goals><goal>stop</goal></goals></execution></executions></plugin>

When working with this plugin you can use an own packaging with a specialized lifecycle in order to keep your pom files small. Three packaging variants are available:

docker : This binds docker:build to the package phase and docker:start / docker:stop to the pre- and post-integration phase respectively. Also docker:push is bound to the deploy phase.

docker-build : Much like the docker packaging, except that there are no integration tests configured by default.

docker-tar : Create a so called Docker tar archive which is used as the artifact and which later can be used for building an image. It contains essentially a Dockerfile with supporting files. See docker:source for more details.

These packaging definitions include the jar lifecycle methods so they are well suited for simple Microservice style projects.

This will create the jar (if any), build the Docker images, start the configured Docker containers, runs the integration tests, stops the configured Docker container when you enter mvn install. With mvn deploy you can additionally push the images to a Docker configuration. Please note the <extensions>true</extensions> which is mandatory when you use a custom lifecycle.

The rest of this manual is now about how to configure the plugin for your images.

3. Global configuration

Global configuration parameters specify overall behavior like the
connection to the Docker host. The corresponding system properties
which can be used to set it from the outside are given in
parentheses.

The docker-maven-plugin uses the Docker remote API so the URL of your
Docker Daemon must somehow be specified. The URL can be specified by
the dockerHost or machine configuration, or by the DOCKER_HOST
environment variable.

The Docker remote API supports communication via SSL and
authentication with certificates. The path to the certificates can
be specified by the certPath or machine configuration, or by the
DOCKER_CERT_PATH environment variable.

Table 1. Global Configuration

Element

Description

Property

apiVersion

Use this variable if you are using an older version of docker not compatible with the current default use to communicate with the server.

docker.apiVersion

authConfig

Authentication information when pulling from or pushing to Docker registry. There is a dedicated section Authentication for how doing security.

autoCreate CustomNetworks

Create automatically Docker networks during docker:start and remove it during docker:stop if you provide a custom network in the run configuration of an image. The default is false.

docker.autoCreateCustomNetworks

autoPull

Decide how to pull missing base images or images to start. This option is deprecated, please use imagePullPolicy instead.

The following values are supported:

on or once: Automatic download any missing images (default)

off : Automatic pulling is switched off always

always : Pull images always even when they already exist locally.

docker.autoPull

certPath

Path to SSL certificate when SSL is used for communicating with the Docker daemon. These certificates are normally stored in ~/.docker/. With this configuration the path can be set explicitly. If not set, the fallback is first taken from the environment variable DOCKER_CERT_PATH and then as last resort ~/.docker/. The keys in this are expected with it standard names ca.pem, cert.pem and key.pem. Please refer to the Docker documentation for more information about SSL security with Docker.

docker.certPath

dockerHost

The URL of the Docker Daemon. If this configuration option is not given, then the optional <machine> configuration section is consulted. The scheme of the URL can be either given directly as http or https
depending on whether plain HTTP communication is enabled or SSL should
be used. Alternatively the scheme could be tcp in which case the
protocol is determined via the IANA assigned port: 2375 for http
and 2376 for https. Finally, Unix sockets are supported by using
the scheme unix together with the filesystem path to the unix socket.
The discovery sequence used by the docker-maven-plugin to determine
the URL is:

value of dockerHost (docker.host)

the Docker host associated with the docker-machine named in <machine>, i.e. the DOCKER_HOST from docker-machine env. See below for more information about Docker machine support. If <machine> is not set, then no docker-machine detection is used.

the value of the environment variable DOCKER_HOST.

/var/run/docker.sock if it is a readable socket (Unix & OS X).

//./pipe/docker_engine if it is a readable named pipe (Windows)

docker.host

filter

In order to temporarily restrict the operation of plugin goals this configuration option can be used. Typically this will be set via the system property docker.filter when Maven is called. The value can be a single image name (either its alias or full name) or it can be a comma separated list with multiple image names. Any name which doesn’t refer an image in the configuration will be ignored.

docker.filter

imagePullPolicy

Specify whether images should be pull when looking for base images while building or images for starting.
This property can take the following values (case insensitive):

IfNotPresent: Automatic download any missing images (default)

Never : Automatic pulling is switched off always

Always : Pull images always even when they already exist locally.

By default a progress meter is printed out on the console, which is omitted when using Maven in batch mode (option -B). A very simplified progress meter is provided when using no color output (i.e. with -Ddocker.useColor=false).

docker.imagePullPolicy

logDate

Date format which is used for printing out container logs. This configuration can be overwritten by individual run configurations and described below. The format is described in Logging.

docker.logDate

logStdout

For all container logging to standard output if set to true, regardless whether a file for log output is specified. See also Logging

Number of parallel connections are allowed to be opened to the Docker Host. For parsing log output, a connection needs to be kept open (as well for the wait features), so don’t put that number to low. Default is 100 which should be suitable for most of the cases.

docker.maxConnections

outputDirectory

Default output directory to be used by this plugin. The default value is target/docker and is only used for the goal docker:build.

docker.target.dir

portPropertyFile

Global property file into which the mapped properties should be written to. The format of this file and its purpose are also described in Port Mapping.

registry

Specify globally a registry to use for pulling and pushing images. See Registry handling for details.

docker.registry

skip

With this parameter the execution of this plugin can be skipped completely.

docker.skip

skipBuild

If set no images will be build (which implies also skip.tag) with docker:build

docker.skip.build

skipPush

If set dont push any images even when docker:push is called.

docker.skip.push

skipRun

If set dont create and start any containers with docker:start or docker:run

docker.skip.run

skipTag

If set to true this plugin won’t add any tags to images that have been built with docker:build.
If set to true this plugin won’t push any tags with docker:push.
If set to true this plugin won’t remove any tags with docker:remove.

docker.skip.tag

skipMachine

Skip using docker machine in any case

docker.skip.machine

sourceDirectory

Default directory that contains the assembly descriptor(s) used by the plugin. The default value is src/main/docker. This option is only relevant for the docker:build goal.

docker.source.dir

useColor

Whether to use colored log output. By default this is switched on when running on a console, off otherwise.

docker.useColor

verbose

Boolean attribute for switching on verbose output on standard output (stdout). This includes detailed information like the build steps when doing a Docker build. Default is false

This plugin supports also Docker machine (which must be installed locally, of course). A Docker machine configuration can be provided with a top-level <machine> configuration section. This configuration section knows the following options:

Table 2. Docker Machine Options

Element

Description

name

Docker machine’s name. Default is default

autoCreate

if set to true then a Docker machine will automatically created. Default is false.

regenerateCertsAfterStart

if set to true then certificates will be regenerated after starting the Docker Machine. This is useful if using the AWS EC2 driver, which will assign machines new IP addresses after each start. Default is false.

createOptions

Map with options for Docker machine when auto-creating a machine. See the docker machine documentation for possible options.

When no Docker host is configured or available as an environment variable, then the configured Docker machine is used. If the machine exists but is not running, it is started automatically. If it does not exists but autoCreate is true, then the machine is created and started. Otherwise, an error is printed. Please note, that a machine which has been created because of autoCreate gets never deleted by docker-maven-plugin. This needs to be done manually if required.

In absence of a <machine> configuration section the Maven property docker.machine.name can be used to provide the name of a Docker machine. Similarly, the property docker.machine.autoCreate can be set to true for creating a Docker machine, too.

You can use the property docker.skip.machine if you want to override the internal detection mechanism to always disable docker machine support.

Example

<!-- Work with a docker-machine --><configuration><machine><name>maven</name><autoCreate>true</autoCreate><createOptions><driver>virtualbox</driver><virtualbox-cpu-count>2</virtualbox-cpu-count></createOptions></machine>
.....
</configuration>

4. Image configuration

The plugin’s configuration is centered around images. These are
specified for each image within the <images> element of the
configuration with one <image> element per image to use.

The <image> element can contain the following sub elements:

Table 3. Image Configuration

Element

Description

name

Each <image> configuration has a mandatory, unique docker
repository name. This can include registry and tag parts, but also placeholder parameters. See below for a detailed explanation.

alias

Shortcut name for an image which can be used for
identifying the image within this configuration. This is used when
linking images together or for specifying it with the global image configuration element.

Element which contains all the configuration aspects when doing a docker:build. This element can be omitted if the image is only pulled from a registry e.g. as support for integration tests like database images.

Element which describe how containers should be
created and run when docker:start is called. If this image is only used a data container (i.e. is supposed only to be mounted as a volume) for exporting artifacts via volumes this section can be missing.

Specification of external configuration as an alternative to this XML based configuration with <run> and <build>. It contains a <type> element specifying the handler for getting the configuration. See External configuration for details.

Name placeholders

When specifying the name you can use several placeholders which are replaced during runtime by this plugin. In addition you can use regular Maven properties which are resolved by Maven itself.

Table 4. Placeholders

Placeholder

Description

%g

The last part of the Maven group name, sanitized so that it can be used as username on GitHub. Only the part after the last dot is used. E.g. for a group id io.fabric8 this placeholder would insert fabric8

%a

A sanitized version of the artefact id so that it can be used as part of an Docker image name. I.e. it is converted to all lower case (as required by Docker)

%v

The project version. Synonym to ${project.version}

%l

If the project version ends with -SNAPSHOT then this placeholder is latest, otherwise its the full version (same as %v)

%t

If the project version ends with -SNAPSHOT this placeholder resolves to snapshot-<timestamp> where timestamp has the date format yyMMdd-HHmmss-SSSS (eg snapshot-). This feature is especially useful during development in oder to avoid conflicts when images are to be updated which are still in use. You need to take care yourself of cleaning up old images afterwards, though.

Either a <build> or <run> section must be present (except when you are using the simple Dockerfile build mode). These are explained in details in the corresponding goal sections.

Note that all goals are orthogonal to each other. For example in order
to start a container for your application you typically have to build
its image before. docker:start does not imply building the image
so you should use it then in combination with docker:build.

5.1. docker:build

This goal will build all images which have a <build> configuration section, or, if the global configuration variable filter (property:
docker.filter) is set, only the images contained in this variable (comma separated) will be built.

There are two different modes how images can be built:

Inline plugin configuration

With an inline plugin configuration all information required to build the image is contained in the plugin configuration. By default its the standard XML based configuration for the plugin but can be switched to a property based configuration syntax as described in the section External configuration. The XML configuration syntax is recommended because of its more structured and typed nature.

When using this mode, the Dockerfile is created on the fly with all instructions extracted from the configuration given.

External Dockerfile or Docker archive

Alternatively an external Dockerfile template or Docker archive can be used. This mode is switched on by using one of these three configuration options within

dockerFileDir specifies a directory containing a Dockerfile that will be used to create the image. The name of the Dockerfile is Dockerfile by default but can be also set with the option dockerFile (see below).

dockerFile specifies a specific Dockerfile path. The Docker build context directory is set to dockerFileDir if given. If not the directory by default is the directory in which the Dockerfile is stored.

dockerArchive specifies a previously saved image archive to load directly. Such a tar archive can be created with docker save. If a dockerArchive is provided, no dockerFile or dockerFileDir must be given.

All paths can be either absolute or relative paths (except when both dockerFileDir and dockerFile are provided in which case dockerFile must not be absolute). A relative path is looked up in ${project.basedir}/src/main/docker by default. You can make it easily an absolute path by using ${project.basedir} in your configuration.

Adding assemblies in Dockerfile mode

Any additional files located in the dockerFileDir directory will also be added to the build context as well.
You can also use an assembly if specified in an assembly configuration.
However, you need to add the files on your own in the Dockerfile with an ADD or COPY command.
The files of the assembly are stored in a build context relative directory maven/ but can be changed by changing the assembly name with the option <name> in the assembly configuration.

E.g. the files can be added with

Example

COPY maven/ /my/target/directory

so that the assembly files will end up in /my/target/directory within the container.

If this directory contains a .maven-dockerignore (or alternatively, a .maven-dockerexclude file), then it is used for excluding files for the build. Each line in this file is treated as a FileSet exclude pattern as used by the maven-assembly-plugin. It is similar to .dockerignore when using Docker but has a slightly different syntax (hence the different name).

If this directory contains a .maven-dockerinclude file, then it is used for including only those files for the build. Each line in this file is also treated as a FileSet exclude pattern as used by the maven-assembly-plugin.

When only a single image should be built with a Dockerfile no XML configuration is needed at all.
All what need to be done is to place a Dockerfile into the top-level module directory, alongside to pom.xml.
You can still configure global aspects in the plugin configuration, but as soon as you add an <image> in the XML configuration, you need to configure also the build explicitly.

The image name is by default set from the Maven coordinates (%g/%a:%l, see Name Placeholders for an explanation of the params which are essentially the Maven GAV)
This name can be set with the property docker.name.

Filtering

fabric8-maven-plugin filters given Dockerfile with Maven properties, much like the maven-resource-plugin does. Filtering is enabled by default and can be switched off with a build config <filter>false</filter>. Properties which we want to replace are specified with the ${..} syntax.
Replacement includes Maven project properties such as ${project.artifactId}, properties set in the build, command-line properties, and system properties. Unresolved properties remain untouched.

This partial replacement means that you can easily mix it with Docker build arguments and environment variable reference, but you need to be careful.
If you want to be more explicit about the property delimiter to clearly separate Docker properties and Maven properties you can redefine the delimiter.
In general, the filter option can be specified the same way as delimiters in the resource plugin.
In particular, if this configuration contains a * then the parts left, and right of the asterisks are used as delimiters.

For example, the default <filter>${*}</filter> parse Maven properties in the format that we know.
If you specify a single character for <filter> then this delimiter is taken for both, the start and the end.
E.g a <filter>@</filter> triggers on parameters in the format @…​@, much like in the maven-invoker-plugin.
Use something like this if you want to clearly separate from Docker builds args.
This form of property replacement works for Dockerfile only.
For replacing other data in other files targeted for the Docker image, please use the maven-resource-plugin or an assembly configuration with filtering to make them available in the docker build context.

Example

The following example uses a Dockerfile in the directory
src/main/docker/demo and replaces all properties in the format @[email protected] within the Dockerfile.

These plugins contain a descriptor META-INF/maven/io.fabric8/dmp-plugin with class names, line-by-line:

io.fabric8.runsh.RunShLoader

During a build with docker:build, those classes are loaded and certain fixed method are called.

The following methods are supported:

Method

Description

addExtraFiles

A static method called by dmp with a single File argument. This will point to a directory docker-extra which can be referenced easily by a Dockerfile or an assembly. A dmp plugin typically will create an own subdirectory to avoid a clash with other dmp-plugins.

If a configured plugin does not provide method of this name and signature, then it will be simply ignored.
Also, no interface needs to be implemented to keep the coupling low.

General purpose startup script fo running Java applications. The dmp plugin creates a target/docker-extra/run-java/run-java.sh which can be included in a Dockerfile (see the example above). See the run-java.sh Documentation for more details.

Check out samples/run-java for a fully working example.

5.1.1. Configuration

All build relevant configuration is contained in the <build> section
of an image configuration. The following configuration options are supported:

Map specifying the value of Docker build args
which should be used when building the image with an external Dockerfile which uses build arguments. The key-value syntax is the same as when defining Maven properties (or labels or env).
This argument is ignored when no external Dockerfile is used. Build args can also be specified as properties as
described in Build Args

buildOptions

Map specifying the build options to provide to the docker daemon when building the image. These options map to the ones listed as query parameters in the
Docker Remote API and are restricted to simple options
(e.g.: memory, shmsize). If you use the respective configuration options for build options natively supported by the build configuration (i.e. nocache, cleanup for forcerm=1 and buildArgs) then these will override any corresponding options given here. The key-value syntax is the same as when defining environment variables or labels as described in Setting Environment Variables and Labels.

cleanup

Cleanup dangling (untagged) images after each build (including any containers created from them). Default is try which tries to remove the old image, but doesn’t fail the build if this is not possible because e.g. the image is still used by a running container. Use remove if you want to fail the build and none if no cleanup is requested.

A command to execute by default (i.e. if no command is provided when a container for this image is started). See Startup Arguments for details.

compression

The compression mode how the build archive is transmitted to the docker daemon (docker:build) and how docker build archives are attached to this build as sources (docker:source). The value can be none (default), gzip or bzip2.

Enable and set the delimiters for property replacements. By default properties in the format ${..} are replaced with Maven properties. You can switch off property replacement by setting this property to false. When using a single char like @ then this is used as a delimiter (e.g @…​@). See Filtering for more details.

from

The base image which should be used for this image. If not given this default to busybox:latest and is suitable for a pure data image.

fromExt

Extended definition for a base image. This field holds a map of defined in <key>value</key> format. The known keys are:

<name> : Name of the base image

A provided <from> takes precedence over the name given here. This tag is useful for extensions of this plugin like the fabric8-maven-plugin which can evaluate the additional information given here.

Don’t use Docker’s build cache. This can be overwritten by setting a system property docker.nocache when running Maven.

optimise

if set to true then it will compress all the runCmds into a single RUN directive so that only one image layer is created.

ports

The exposed ports which is a list of <port> elements, one for each port to expose. Whitespace is trimmed from each element and empty elements are ignored. The format can be either pure numerical ("8080") or with the protocol attached ("8080/tcp").

runCmds

Commands to be run during the build process. It contains run elements which are passed to the shell. Whitespace is trimmed from each element and empty elements are ignored. The run commands are inserted right after the assembly and after workdir into the Dockerfile. This tag is not to be confused with the <run> section for this image which specifies the runtime behaviour when starting containers.

skip

if set to true disables building of the image. This config option is best used together with a maven property

skipTag

If set to true this plugin won’t add any tags to images. Property: docker.skip.tag

tags

List of additional tag elements with which an image is to be tagged after the build. Whitespace is trimmed from each element and empty elements are ignored.

user

User to which the Dockerfile should switch to the end (corresponds to the USER Dockerfile directive).

volumes

List of volume elements to create a container volume. Whitespace is trimmed from each element and empty elements are ignored.

workdir

Directory to change to when starting the container.

From this configuration this Plugin creates an in-memory Dockerfile,
copies over the assembled files and calls the Docker daemon via its
remote API.

Assembly name, which is maven by default. This name is used for the archives and directories created during the build. This directory holds the files specified by the assembly. If an external Dockerfile is used than this name is also the relative directory which contains the assembly files.

targetDir

Directory under which the files and artifacts contained in the assembly will be copied within the container. The default value for this is /<assembly name>, so /maven if name is not set to a different value. This option has no meaning when an external Dockerfile is used.

Alias to a predefined assembly descriptor. The available aliases are also described in Assembly Descriptor below.

dockerFileDir

Directory containing an external Dockerfile. This option is deprecated, please use <dockerFileDir> directly in the <build> section.

exportTargetDir

Specification whether the targetDir should be exported as a volume. This value is true by default except in the case the targetDir is set to the container root (/). It is also false by default when a base image is used with from since exporting makes no sense in this case and will waste disk space unnecessarily.

ignorePermissions

Specification if existing file permissions should be ignored
when creating the assembly archive with a mode dir. This value is false by default. This property is deprecated, use a permissions of ignore instead.

mode

Mode how the how the assembled files should be collected:

dir : Files are simply copied (default),

tar : Transfer via tar archive

tgz : Transfer via compressed tar archive

zip : Transfer via ZIP archive

The archive formats have the advantage that file permission can be preserved better (since the copying is independent from the underlying files systems), but might triggers internal bugs from the Maven assembler (as it has been reported in #171)

permissions

Permission of the files to add:

ignore to use the permission as found on files regardless on any
assembly configuration

keep to respect the assembly provided permissions, exec for setting the executable bit on all files (required for Windows when using an assembly mode dir)

User and/or group under which the files should be added. The user must already exist in the base image.

It has the general format user[:group[:run-user]]. The user and group can be given either as numeric user- and group-id or as names. The group id is optional.

If a third part is given, then the build changes to user root before changing the ownerships, changes the ownerships and then change to user run-user which is then used for the final command to execute. This feature might be needed, if the base image already changed the user (e.g. to 'jboss') so that a chown from root to this user would fail.

For example, the image jboss/wildfly use a "jboss" user under which all commands are executed. Adding files in Docker always happens under the UID root. These files can only be changed to "jboss" is the chown command is executed as root. For the following commands to be run again as "jboss" (like the final standalone.sh), the plugin switches back to user jboss (this is this "run-user") after changing the file ownership. For this example a specification of
jboss:jboss:jboss would be required.

In the event you do not need to include any artifacts with the image, you may safely omit this element from the configuration.

Assembly Descriptor

With using the inline, descriptor or descriptorRef option
it is possible to bring local files, artifacts and dependencies into
the running Docker container. A descriptor points to a file
describing the data to put into an image to build. It has the same
format as for creating assemblies with the
maven-assembly-plugin with following exceptions:

<formats> are ignored, the assembly will allways use a directory
when preparing the data container (i.e. the format is fixed to
dir)

The <id> is ignored since only a single assembly descriptor is
used (no need to distinguish multiple descriptors)

Also you can inline the assembly description with a inline description
directly into the pom file. Adding the proper namespace even allows for
IDE autocompletion. As an example, refer to the profile inline in
the data-jolokia-demo 's pom.xml.

Alternatively descriptorRef can be used with the name of a
predefined assembly descriptor. The following symbolic names can be
used for descriptorRef:

Table 8. Predefined Assembly Descriptors

Assembly Reference

Description

artifact-with-dependencies

Attaches project’s artifact and all its dependencies. Also, when a classpath file exists in the target directory, this will be added to.

artifact

Attaches only the project’s artifact but no dependencies.

project

Attaches the whole Maven project but with out the target/ directory.

rootWar

Copies the artifact as ROOT.war to the exposed directory. I.e. Tomcat will then deploy the war under the root context.

will add the created artifact with the name ${project.build.finalName}.${artifact.extension} and all jar dependencies in the the targetDir (which is /maven by default).

All declared files end up in the configured targetDir (or /maven by default) in the created image.

Maven peculiarities when including the artifact

If the assembly references the artifact to build with this pom, it is required that the package phase is included in the run. Otherwise the artifact file, can’t be found by docker:build. This is an old outstanding issue of the assembly plugin which probably can’t be fixed because of the way how Maven works. We tried hard to workaround this issue and in 90% of all cases, you won’t experience any problem. However, when the following warning happens which might lead to the given error:

[WARNING] Cannot include project artifact: io.fabric8:helloworld:jar:0.20.0; it doesn't have an associated file or directory.
[WARNING] The following patterns were never triggered in this artifact inclusion filter:
o 'io.fabric8:helloworld'
[ERROR] DOCKER> Failed to create assembly for docker image (with mode 'dir'): Error creating assembly archive docker: You must set at least one file.

then you have two options to fix this:

Call mvn package docker:build to explicitly run "package" and "docker:build" in a chain.

Bind build to an to an execution phase in the plugin’s definition. By default docker:build will bind to the install phase is set in an execution. Then you can use a plain mvn install for building the artifact and creating the image.

In the following example a dependency from the pom.xml is included and
mapped to the name jolokia.war. With this configuration you will end
up with an image, based on busybox which has a directory /maven
containing a single file jolokia.war. This volume is also exported
automatically.

Another container can now connect to the volume an 'mount' the
/maven directory. A container from consol/tomcat-7.0 will look
into /maven and copy over everything to /opt/tomcat/webapps before
starting Tomcat.

If you are using the artifact or artifact-with-dependencies descriptor, it is
possible to change the name of the final build artifact with the following:

Example

<build><finalName>your-desired-final-name</finalName>
...
</build>

Please note, based upon the following documentation listed here, there is no guarantee the plugin creating your artifact will honor it in which case you will need to use a custom descriptor like above to achieve the desired naming.

Currently the jar and war plugins properly honor the usage of finalName.

5.1.3. Startup Arguments

Using entryPoint and cmd it is possible to specify the entry point
or cmd for a container.

The difference is, that an entrypoint is the command that always be executed, with the cmd as argument. If no entryPoint is provided, it defaults to /bin/sh -c so any cmd given is executed with a shell. The arguments given to docker run are always given as arguments to the
entrypoint, overriding any given cmd option. On the other hand if no extra arguments are given to docker run the default cmd is used as argument to entrypoint.

5.1.4. Build Args

As described in section Configuration for external Dockerfiles Docker build arg can be used. In addition to the
configuration within the plugin configuration you can also use properties to specify them:

Set a system property when running Maven, eg.: -Ddocker.buildArg.http_proxy=http://proxy:8001. This is especially
useful when using predefined Docker arguments for setting proxies transparently.

Set a project property within the pom.xml, eg.:

Example

<docker.buildArg.myBuildArg>myValue</docker.buildArg.myBuildArg>

Please note that the system property setting will always override the project property. Also note that for all properties which are not Docker predefined properties, the external Dockerfile must contain an ARGS instruction.

5.1.5. Healthcheck

Healthchecks has been introduced since Docker 1.12 and are a way to tell Docker how to test a container to check that it’s still working. With a health check you specify a command which is periodically executed and checked for its return value. If the healtcheck return with an exit 0 the container is considered to be healthy, if it returns with 1 then the container is not working correctly.

The healtcheck configuration can have the following options

Table 10. Healthcheck Configuration

Element

Description

cmd

Command to execute, which can be given in an shell or exec format as described in Startup Arguments.

interval

Interval for how often to run the healthcheck. The time is specified in seconds, but a time unit can be appended to change this.

mode

Mode of the healthcheck. This can be cmd which is the default and specifies that the health check should be executed. Or none to disable a health check from the base image. Only use this option with none for disabling some healthcheck from the base image.

retries

How many retries should be performed before the container is to be considered unhealthy.

startPeriod

Initialization time for containers that need time to bootstrap. Probe failure during that period will not be counted towards the maximum number of retries. However, if a health check succeeds during the start period, the container is considered started and all consecutive failures will be counted towards the maximum number of retries. Given in seconds, but another time unit can be appended.

timeout

Timeout after which healthckeck should be stopped and considered to have failed. Given in seconds, but another time unit can be appended.

The following example queries an URL every 10s as an healthcheck:

Example

<healthCheck><!-- Check every 5 minutes --><interval>5m</interval><!-- Fail if no response after 3 seconds --><timeout>3s</timeout><!-- Allow 30 minutes for the container to start before being flagged as unhealthy --><startPeriod>30m</startPeriod><!-- Fail 3 times until the container is considerd unhealthy --><retries>3</retries><!-- Command to execute in shell form --><cmd>curl -f http://localhost/ || exit 1</cmd></healthCheck>

5.2. docker:start

This goal creates and starts docker containers. This goals evaluates the configuration’s <run> section of all given (and enabled images).

Also you can specify docker.follow as system property so that the docker:start will never return but block until CTRL-C is pressed. That similar to the option -i for docker run. This will automatically switch on showLogs so that you can see what is happening within the container. Also, after stopping with CTRL-C, the container is stopped (but not removed so that you can make postmortem analysis). docker:run is an alias for docker:start with docker.follow enabled.

By default container specific properties are exposed as Maven properties. These properties have the format docker.container.<alias>.<prop> where <alias> is the name of the container (see below) and <prop> is one of the following container properties:

Table 11. Properties provided

Property

Description

ip

Internal IP address of the container.

id

Container id

net.<network>.ip

Internal IP address of the container in the specified custom network. This works only for custom networks.

Instead of the <alias> a fixed property key can be configured in the image’s <run> configuration with the option exposedPropertyKey.

For example the Maven property docker.container.tomcat.ip would hold the Docker internal IP for a container with an alias "tomcat". You can set the global configuration exposeContainerInfo to an empty string to not expose container information that way or to a string for an other prefix than docker.container.

5.2.1. Configuration

In addition to the Global configuration, this goal supports the following global configuration options.

Table 12. Start options

Element

Description

Property

showLogs

In order to switch on globally the logs showLogs can be used as global configuration (i.e. outside of <images>). If set it will print out all standard
output and standard error messages for all containers started. As value the images for which logs should be shown can be given as a comma separated list.
This is probably most useful when used from the command line as system property docker.showLogs.

docker.showLogs

startParallel

Starts docker images in parallel while dependencies expressed as Link or dependsOn are respected. This option can significantly reduce the startup time because independent containers do not need to wait for each other.

Environment variables as subelements which are set during startup of the container. They are specified in the typical maven property format as described Environment and Labels.

envPropertyFile

Path to a property file holding environment variables. If given, the variables specified in this property file overrides the environment variables specified in the configuration.

extraHosts

List of host elements in the form host:ip to add to the container’s /etc/hosts file. Additionally, you may specify a host element in the form host:host to have the right side host ip address resolved at container startup.

exposedPropertyKey

Set the property part for the exposed container properties as described above. This will take precedence of the image’s alias which is the default value. For example, when this property is set to jboss, then for this container its IP address is exposed in Maven property docker.container.jboss.ip regardless how the image is named.

hostname

Hostname of the container

imagePullPolicy

Specific pull policy for downloading the image. This overwrites any global pull policy. See the global imagePullPolicy configuration option for the possible values and the default.

If you put this configuration into profiles you can easily create various test variants with a single image (e.g. by switching the JDK or whatever).

It is also possible to set the environment variables from the outside of the plugin’s configuration with the parameter envPropertyFile. If given, this property file is used to set the environment variables where the keys and values specify the environment variable. Environment variables specified in this file override any environment variables specified in the configuration.

5.2.3. Port Mapping

The <ports> configuration contains a list of port mappings. Whitespace is trimmed from each element and empty elements are ignored. Each mapping has multiple parts, each separate by a colon. This is equivalent to the port mapping when using the Docker CLI with option -p.

A port stanza may take one of the following forms:

Table 14. Port mapping format

Format

Description

18080:8080

Tuple consisting of two numeric values separated by a :. This form will result in an explicit mapping between the docker host and the corresponding port inside the container. In the above example, port 18080 would be exposed on the docker host and mapped to port 8080 in the running container.

host.port:80

Tuple consisting of a string and a numeric value separated by a :. In this form, the string portion of the tuple will correspond to a Maven property. If the property is undefined when the start task executes, a port will be dynamically selected by Docker in the ephemeral port range and assigned to the property which may then be used later in the same POM file. The ephemeral port range is configured by the /proc/sys/net/ipv4/ip_local_port_range kernel parameter, which typically ranges from 32678 to 61000. If the property exists and has numeric value, that value will be used as the exposed port on the docker host as in the previous form. In the above example, the docker service will elect a new port and assign the value to the property host.port which may then later be used in a property expression similar to <value>${host.port}</value>. This can be used to pin a port from the outside when doing some initial testing similar to mvn -Dhost.port=10080 docker:start

bindTo:host.port:80

Tuple consisting of two strings and a numeric value separated by a :. In this form, bindTo is an ip address on the host the container should bind to. As a convenience, a hostname pointing to the docker host may also be specified. The container will fail to start if the hostname can not be resolved.

+host.ip:host.port:80

Tuple consisting of two strings and a numeric value separated by a :. In this form, the host ip of the container will be placed into a Maven property name host.ip. If docker reports that value to be 0.0.0.0, the value of docker.host.address will be substituted instead. In the event you want to use this form and have the container bind to a specific hostname/ip address, you can declare a Maven property of the same name (host.ip in this example) containing the value to use. host:port works in the same way as described above.

Another useful configuration option is portPropertyFile which can be used to write out the container’s host ip and any dynamic ports that have been resolved. The keys of this property file are the property names defined in the port mapping configuration and their values those of the corresponding docker attributes.

This property file might be useful with tests or with other maven plugins that will be unable to use the resolved properties because they can only be updated after the container has started and plugins resolve their properties in an earlier lifecycle phase.

If you don’t need to write out such a property file and thus don’t need to preserve the property names, you can use normal maven properties as well. E.g. ${host.var}:${port.var}:8080 instead of
+host.var:port.var:8080.

5.2.4. Links

The <links> configuration contains a list of containers that should
be linked to this container according to Docker Links. Each link can have two parts where the optional right side is separated by a : and will be used as the name in the environment variables and the left side refers to the name of the container linking to. This is equivalent to the linking when using the Docker CLI --link option.

Example for linking to a container with name or alias postgres :

Example

<links><link>postgres:db</link></links>

This will create the following environment variables, given that the postgres image exposes TCP port 5432:

Additionally, each <link> element can specify a comma separated set of links. Comma (and whitespace) can be used to separate links since valid docker link names/aliases contain only characters, digits, underscores, periods and dashes.

Example

<links><link>postgres:db, search, saml:identity</link></links>

If you wish to link to existing containers not managed by the plugin, you may do so by specifying the container name obtained via docker ps in the configuration.

Please note that the link behaviour also depends on the network mode selected. Links as described are referred to by Docker as legacy links and might vanish in the future. For custom networks no environments variables are set and links create merely network aliases for the linked container. To express start order dependencies using custom networks refer to the dependsOn configuration.

5.2.5. Network

The <network> element in the <run> configuration section can be used to configure the network mode of the container. This is now the preferred way for linking containers together. It knows the following sub elements:

Table 15. Network configuration

Element

Description

mode

The network mode, which can be one of the following values:

bridge : Bridged mode with the default Docker bridge (default)

host : Share the Docker host network interfaces

container : Connect to the network of the specified container. The name of the container is taken from the <name> element.

custom : Use a custom network, which must be created before by using docker network create. Alternatively you can set the docker.autoCreateCustomNetworksglobal configuration parameter to true to automatically create custom networks. Custom networks are available for Docker 1.9 and newer. For more about the networking options please refer to the Docker documentation.

none : No network will be setup.

name

For mode container this is the container name, which is this image alias. For Mode custom this is the name of the custom network.

alias

One or more alias element can be provided which gives a way for a container to be discovered by alternate names by any other container within the scope of a particular network. This configuration only has effect for when the network mode is custom. More than one alias can be given by providing multiple entries.

If no mode is given but a name, then a custom network mode is assumed. For the simple modes which does not take an argument (none, bridge or host) a single <net>mode</net> can be used as alternative to using <network> with a <mode> subelement.

5.2.6. Depends-On

Custom networks do not provide a mechanism like <links> to express strong links between containers. They are normally not required because docker ensures that all containers within the same custom network can eventually resolve each other via DNS.

Your containers should preferably be able to deal with temporarily unresolvable dependencies but in some cases it is helpful to be able to rely the availability of other infrastructure containers.

The <dependsOn> configuration can be used to expresses custom network dependencies between your containers. docker:start will ensure that all dependencies a container depends on are completely started (fulfilling all <wait> conditions) before the depending container is started.

Additionally, each <container> element can specify a comma separated set of containers. Comma (and whitespace) can be used to separate containers since valid docker container names contain only characters, digits, underscores, periods and dashes.

5.2.7. Restart Policy

Specify the behavior to apply when the container exits. These values can be specified withing a <restartPolicy> section with the following sub-elements:

Table 16. Restart Policy configuration

Element

Description

name

Restart policy name, choose from:

always (v1.15) always restart

on-failure (v1.15) restart on container non-exit code of zero

retry

If on-failure is used, controls max number of attempts to restart before giving up.

The behavior to apply when the container exits. The value is an object with a name property of either "always" to always restart or "on-failure" to restart only when the container exit code is non-zero. If on-failure is used, MaximumRetryCount controls the number of times to retry before giving up. The default is not to restart. (optional)

5.2.8. Volumes

A container can bind (or "mount") volumes from various source when starting up: Either from a directory of the host system or from another container which exports one or more directories. The mount configuration is specified within a <volumes> section of the run configuration. It can contain the following sub elements:

Table 17. Volume configuration

Element

Description

from

List of <image> elements which specify image names or aliases of containers whose volumes should be imported.

bind

List of <volume> specifications (or host mounts). Use /path to create and expose a new volume in the container, /host_path:/container_path to mount a host path into the container and /host_path:/container_path:ro to bind it read-only.

In this example the container creates a new volume named /logs on the container and mounts /opt/host_export from the host as /opt/container_import on the container. In addition all exported volumes from the container which has been created from the image jolokia/docker-demo are mounted directly into the container (with the same directory names under which the exporting container exposes these directories). This image must be also configured for this plugin. Instead of the full image name, an alias name can be used, too.

You can use Maven variables in the path specifications. This should even work for boot2docker and docker-machine:

If you wish to mount volumes from an existing container not managed by the plugin, you may do by specifying the container name obtained via docker ps in the configuration.

5.2.9. Wait

While starting a container is it possible to block the execution until
some condition is met. These conditions can be specified within a
<wait> section which the following sub-elements:

Table 18. Wait configuration

Element

Description

http

HTTP ping check which periodically polls an URL. It knows the following sub-elements:

url holds an URL and is mandatory

method Optional HTTP method to use.

status Status code which if returned is considered to be a successful ping. This code can be given either as a single number (200) or as a range (200..399). The default is 200..399

allowAllHosts If url is an HTTPS url and this option is set, then server certificates are not validated. By default they are checked for a proper CA signature.

log

Regular expression which is applied against the log
output of an container and blocks until the pattern is matched. You can use (?s) in the pattern to switch on multi line matching.

time

Time in milliseconds to block.

kill

Time in milliseconds between sending SIGTERM and SIGKILL when stopping a container. Since docker itself uses second granularity, you should use at least 1000 milliseconds.

shutdown

Time to wait in milliseconds between stopping a container and removing it. This might be helpful in situation where a Docker croaks with an error when trying to remove a container to fast after it has been stopped.

exec

Commands to execute during specified lifecycle of the container. It knows the following sub-elements:

postStart Command to run after the above wait criteria has been met

preStop Command to run before the container is stopped.

breakOnError If set to true then break the build if a postStart or preStop command exits with an return code other than 0, otherwise only print an error message.

tcp

TCP port check which periodically polls given tcp ports. It knows the following sub-elements:

mode can be either mapped which uses the mapped ports or direct in which case the container ports are addressed directly. In the later case the host field should be left empty in order to select the container ip (which must be routed which is only the case when running on the Docker daemon’s host directly). Default is direct when host is localhost, mapped otherwise. The direct mode might help when a so called user-proxy is enabled on the Docker daemon which makes the mapped ports directly available even when the container is not ready yet.

host is the hostname or the IP address. It defaults to ${docker.host.address} for a mapped mode and the container ip address for the direct mode.

ports is a list of TCP ports to check. These are supposed to be the container internal ports.

healthy

Check that waits until the container health state becomes healthy. A container is considered healthy when its configured healtcheck succeeds.

As soon as one condition is met the build continues. If you add a <time> constraint this works more or less as a timeout for other conditions. The build will abort if you wait on an url or log output and reach the timeout. If only a <time> is specified, the build will wait that amount of milliseconds and then continues.

This setup will wait for the given URL to be reachable but ten seconds at most. Additionally, it will wait for the TCP ports 3306 and 9999. Also, when stopping the container after integration tests, the build wait for 500 ms before it tries to remove the container (if not keepContainer or keepRunning is used). You can use maven properties in each condition, too. In the example, the ${host.port} property is probably set before within a port mapping section.

The property ${docker.host.address} is set implicitly to the address of the Docker host. This host will be taken from the docker.host configuration if HTTP or HTTPS is used. If a Unix socket is used for communication with the docker daemon, then localhost is assumed. You can override this property always by setting this Maven property explicitly.

5.2.10. Logging

When running containers the standard output and standard error of the container can be printed out. Several options are available for configuring the log output:

Table 19. Logging configuration

Element

Description

enabled

If set to false log output is disabled. This is useful if you want to disable log output by default but want to use the other configuration options when log output is switched on on the command line with -Ddocker.showLogs. Logging is enabled by default if a <log> section is given.

prefix

Prefix to use for the log output in order to identify the container. You can use placeholders in the prefix which are replaced on the fly:

%a: Alias of the image, or, if not set, the short container id.

%c: Short container id (i.e. the first 6 chars of the container id

%C: The full container id

%n: The image name

%z: An empty string

By default the format is "%a> ".

date

Dateformat to use for log timestamps. If <date> is not given no timestamp will be shown. The date specification can be either a constant or a date format. The recognized constants are:

NONE Switch off timestamp output. Useful on the command line
(-Ddocker.logDate=NONE) for switching off otherwise enabled
logging.

DEFAULT A default format in the form HH:mm:ss.SSS

MEDIUM Joda medium date time format

SHORT Joda short date time format

LONG Joda long date time format

ISO8601 Full ISO-8601 formatted date time with milliseconds

As an alternative a date-time format string as recognized by
JodaTime is possible. In order to set a consistent date format, the global configuration parameter logDate can be used.

color

Color used for coloring the prefix when coloring is enabled (i.e. if running in a console and useColor is set). The available colors are YELLOW, CYAN, MAGENTA, GREEN, RED, BLUE. If coloring is enabled and now color is provided a color is picked for you.

file

Path to a file to which the log output is written. This file is overwritten for every run and colors are switched off.

driver

Section which can specify a dedicated log driver to use. A <name> tag within this section depicts the logging driver with the options specified in <opts>. See the example below for how to use this.

Example

<log><prefix>TC</prefix><date>default</date><color>cyan</color></log>

The following example switches on the gelflogging driver .
This is equivalent to the options --log-driver=gelf --log-opt gelf-address=udp://localhost:12201 when using docker run.

5.3. docker:stop

Stops and removes a docker container. This goal stops every container started with <docker:start> either during the same build (e.g. when bound to lifecycle phases when doing integration tests) or for containers created by a previous call to <docker:start>

If called within the same build run, only the containers that were explicitly started during the run will be stopped. Existing containers started using docker:start for the project will not be affected.

If called as a separate invocation, the plugin will stop and remove any container it finds whose image is defined in the project’s configuration. Any existing containers found running whose image name matches but were not started by the plugin will not be affected.

In case the naming strategy for an image is alias (i.e. the container name is set to the given alias), then only the container with this alias is stopped. Other containers originating from the same image are not touched.

It should be noted that any containers created prior to version 0.13.7 of the plugin may not be stopped correctly by the plugin because the label needed to tie the container to the project may not exist. Should this happen, you will need to use the Docker CLI to clean up the containers and/or use the docker.allContainers option listed below.

For tuning what should happen when stopping there are four global parameters which are typically used as system properties:

Table 20. Stop configuration

Element

Description

Parameter

keepContainer

If set to true not destroy container after they have been stopped. Default is false.

docker.keepContainer

keepRunning

If set to true actually don’t stop the container. This apparently makes only sense when used on the command line when doing integration testing (i.e. calling docker:stop during a lifecycle binding) so that the container are still running after an integration test. This is useful for analysis of the containers (e.g. by entering it with docker exec).

docker.keepRunning

removeVolumes

If set to true will remove any volumes associated to the container as well. This option will be ignored if either keepContainer or keepRunning are true.

docker.removeVolumes

allContainers

Stops and removes any container that matches an image defined in the current project’s configuration. This was the default behavior of the plugin prior up to version 0.13.6

docker.allContainers

Example

$ mvn -Ddocker.keepRunning clean install

5.4. docker:push

This goal uploads images to the registry which have a <build> configuration section. The images to push can be restricted with
the global option filter (see Global Configuration for details). The registry to push is by default docker.io but can be specified as part of the images’s name name the Docker way. E.g. docker.test.org:5000/data:1.5 will push the image data with tag 1.5 to the registry docker.test.org at port 5000. Security information (i.e. user and password) can be specified in multiple ways as described in section Authentication.

By default a progress meter is printed out on the console, which is omitted when using Maven in batch mode (option -B). A very simplified progress meter is provided when using no color output (i.e. with -Ddocker.useColor=false).

How often should a push be retried before giving up. This useful for flaky registries which tend to return 500 error codes from time to time. The default is 0 which means no retry at all.

docker.push.retries

5.5. docker:watch

When developing and testing applications you will often have to rebuild Docker images and restart containers. Typing docker:build and docker:start all the time is cumbersome. With docker:watch you can enable automatic rebuilding of images and restarting of containers in case of updates.

docker:watch is the top-level goal which performs these tasks. There are two watch modes, which can be specified in multiple ways:

build : Automatically rebuild one or more Docker images when one of the files selected by an assembly changes. This works for all files included directly in assembly.xml but also for arbitrary dependencies.

Example

$ mvn package docker:build docker:watch -Ddocker.watchMode=build

This mode works only when there is a <build> section in an image configuration. Otherwise no automatically build will be triggered for an image with only a <run> section. Note that you need the package phase to be executed before otherwise any artifact created by this build can not be included into the assembly. As described in the section about docker:start this is a Maven limitation.
* run : Automatically restart container when their associated images changes. This is useful if you pull a new version of an image externally or especially in combination with the build mode to restart containers when their image has been automatically rebuilt. This mode works reliably only when used together with docker:start.

Example

$ mvn docker:start docker:watch -Ddocker.watchMode=run

both : Enables both build and run. This is the default.

none : Image is completely ignored for watching.

copy : Copy changed files into the running container. This is the fast way to update a container, however the target container must support hot deploy, too so that it makes sense. Most application servers like Tomcat supports this.

The mode can also be both or none to select both or none of these variants, respectively. The default is both.

docker:watch will run forever until it is interrupted with CTRL-C after which it will stop all containers. Depending on the configuration parameters keepContainer and removeVolumes the stopped containers with their volumes will be removed, too.

When an image is removed while watching it, error messages will be printed out periodically. So don’t do that ;-)

Dynamically assigned ports stay stable in that they won’t change after a container has been stopped and a new container is created and started. The new container will try to allocate the same ports as the previous container.

If containers are linked together network or volume wise, and you update a container which other containers dependent on, the dependant containers are not restarted for now. E.g. when you have a "service" container accessing a "db" container and the "db" container is updated, then you "service" container will fail until it is restarted, too.

A future version of this plugin will take care of restarting
these containers, too (in the right order), but for now you would have
to do this manually.

This maven goal can be configured with the following top-level parameters:

Table 22. Watch configuration

Element

Description

Property

watchMode

Watch mode specifies what should be watched

build : Watch changes in the assembly and rebuild the image in
case

run : Watch a container’s image whether it changes and restart
the container in case

copy : Changed files are copied into the container. The container can be either running or might be already exited (when used as a data container linked into a platform container). Requires Docker >= 1.8.

both : build and run combined

none : Neither watching for builds nor images. This is useful if
you use prefactored images which won’t be changed and hence don’t
need any watching. none is best used on an per image level, see
below how this can be specified.

docker.watchMode

watchInterval

Interval in milliseconds how often to check for changes, which must be larger than 100ms. The default is 5 seconds.

docker.watchInterval

watchPostGoal

A maven goal which should be called if a rebuild or a restart has been performed. This goal must have the format <pluginGroupId>:<pluginArtifactId>:<goal> and the plugin must be configured in the pom.xml. For example a post-goal io.fabric8:fabric8:delete-pods will trigger the deletion of PODs in Kubernetes which in turn triggers are new start of a POD within the Kubernetes cluster. The value specified here is the the default post goal which can be overridden by <postGoal> in a <watch> configuration.

watchPostExec

A command which is executed within the container after files are copied into this container when watchMode is copy. Note that this container must be running.

keepRunning

If set to true all container will be kept running after docker:watch has been stopped. By default this is set to false.

docker.keepRunning

keepContainer

As for docker:stop, if this is set to true (and keepRunning is disabled) then all container will be removed after they have been stopped. The default is true.

docker.keepContainer

removeVolumes

if set to true will remove any volumes associated to the container as well. This option will be ignored if either keepContainer or keepRunning are true.

Each image can be configured for having individual watch mode. These take precedence of the global watch mode. The mode specified in this configuration takes precedence over the globally specified mode.

interval

Watch interval can be specified in milliseconds on image level. If given this will override the global watch interval.

postGoal

Post Maven plugin goal after a rebuild or restart. The value here must have the format <pluginGroupId>:<pluginArtifactId>:<goal> (e.g. io.fabric8:fabric8:delete-pods)

postExec

Command to execute after files are copied into a
running container when mode is copy.

You can build the service image, start up all containers and go into a watch loop. Again, you need the package phase in order that the assembly can find the artifact build by this project. This is a Maven limitation. The db image will never be watch since it assumed to not change while watching.

5.6. docker:remove

This goal can be used to clean up images and containers. By default all images with a build configuration are removed.
You can tune this by setting the property removeMode (property: docker.removeMode) to one of the following values:

Previously, this could be tuned also by providing the property removeAll which indicates to remove all images managed by this build. Otherwise only data images were delete before 0.24.0. removeAll is deprecated and will be removed soone. Please use removeMode instead.

As with the other goals, the configuration image can be used to tune the images to remove. All containers belonging to the images are removed as well as the all tags assigned to this image

Considering three images 'db','tomcat' and 'data' where 'data' is the only image with a build configuration:

mvn docker:remove will remove 'data'

mvn -Ddocker.removeMode=all docker:remove will remove all three images

5.7. docker:logs

With this goal it is possible to print out the logs of containers
started from images configured in this plugin. By default only the
latest container started is printed, but this can be changed with a
property. The format of the log output is influenced by run
configuration of the configured images. The following system
properties can the behaviour of this goal:

Table 26. Logging options

Property

Description

docker.logAll

If set to true the logs of all containers created from images configured for this plugin are printed. The container id is then prefixed before every log line. These images can contain many containers which are already stopped. It is probably a better idea to use docker logs diretly from the command line.

docker.follow

If given will wait for subsequent log output until CRTL-C is pressed. This is similar to the behaviour of docker logs -f (or tail -f).

docker.filter

Filter to restrict the set of images for which log should be fetched. This can be a comma separated list of image or alias names.

5.8. docker:source

The docker:source target can be used to attach a docker build archive containing the Dockerfile and all added files to the Maven project with a certain classifier. It reuses the configuration from [docker:build> ].

By default, only the first image configuration is used for creating the source archive.
You can export all image configurations by setting the sourceMode configuration to all:

For exporting all image configurations, docker:source uses the image’s alias as part of the classifier, so it is mandatory that the alias is set for
this goal to work when all images should be exported this way.
The classifier is calculated as docker-<alias> so when the alias is set to service, then the classifier is docker-service.

If you only export the first image configuration (which is the default), then the classifier is just docker (without alias).

docker:source can be attached to a Maven execution phase, which is generate-sources by default.

For example, this configuration will attach the docker build archive to the artifacts to store in the repository:

If not bound to an execution phase, docker:source requires that the artifact has been created so you call it best together with package

5.9. docker:save

The docker:save target saves an image defined in the build configuration to a local file, analogous to docker save.
If the option saveFile is not set, the file name is calculated automatically:

If saveAlias is used then the file is stored as target/<alias>-<project version>.tar.gz

Otherwise the archive is stored as target/<image name without registry and user part>-<image tag>.tar.gz

Please note that the exported image contains all image layers and can be quite large (also, it takes a bit to export the image).

Table 27. Save options

Element

Description

Property

saveName

The name of the image configuration to save. Must not be used together with alias.

docker.save.name

saveAlias

The alias of the image configuration to save. Must not be used together with name.

docker.save.alias

saveFile

The filename to save.

docker.save.file or docker.file or file

skipSave

A boolean flag whether to skip execution of the goal.

docker.skip.save

5.10. docker:volume-create

This goals creates one or more standalone Docker volume, which can be referenced in a docker:start configuration for linking to a volume during runtime.
Each volume has therefore a unique and referenceable name. Beside the volume driver and driver options can be specified.

Volume driver to use. By default the driver local is used which is created on the local file system. Please refer to your Docker installation which additional drivers are available.

opts

Driver specific options passed in as custom <key>value</key> where its maps to key=value pairs for driver options as they can be provided from the Docker CLI, too. Each volume driver supports different options. The options supported by the local driver are the well known Linux mount options.

labels

Labels given as <key>value</key> similar to image labels described in Environment and Labels. These labels are used to tag the volumes themselves.

5.11. docker:volume-remove

This goals is the counterpart to docker:volume-create and removes a volume.
Docker volumes are configured outside of Docker images, but can be referenced by them.
The configuration is the same as for docker:volume-create

The configuration is quite simple. Only the name of the volume to delete is required.

Table 29. Volume configuration

Element

Description

name

Name of the volume

6. External Configuration

For special configuration needs, there is the possibility to get the
runtime and build configuration from places outside the plugin’s
configuration. This is done with the help of <external>
configuration sections which at least has a <type> subelement. This
<type> element selects a specific so called "handler" which is
responsible for creating the full image configuration. A handler can
decide to use the <run> and <build> configuration which could
be provided in addition to this <external> section or it can decide
to completely ignore any extra configuration option.

A handler can also decide to expand this single image configuration to
a list of image configurations. The image configurations resulting
from such a external configuration are added to the regular<image> configurations without an <external> section.

The available handlers are described in the following.

6.1. Properties

For simple needs the image configuration can be completely defined via
Maven properties which are defined outside of this plugin’s
configuration. Such a property based configuration can be selected
with an <type> of properties. As extra configuration a prefix for the
properties can be defined which by default is docker.

For single-image configurations it is also possible to active property
based configuration via an externally set property.

By default, property based configuration uses only properties, ignoring
any <build> and <run> sections. To combine values from both sources,
use the property mode configuration.

Properties are read from the Maven project (defined in <properties> or global
Maven configuration from settings.xml) and, since 0.25.0, from any -D
flags given to Maven (takes priority over project properties).

Example

<image><external><type>properties</type><prefix>docker</prefix><!-- this is the default --><mode>only</mode><!-- this is the default --></external></image>

Given this example configuration a single image configuration is built
up from the following properties, which correspond to the corresponding
values in the <build> and <run> sections. A build configuration is only created
when a docker.from or a docker.fromExt is set.

Table 30. External properties

docker.alias

Alias name

docker.args.BUILDVAR

Set the value of a build variable. The syntax is the same as for specifying environment variables (see below).

docker.assembly.baseDir

Directory name for the exported artifacts as described in an assembly (which is /maven by default).

docker.assembly.descriptor

Path to the assembly descriptor when building an image

docker.assembly.descriptorRef

Name of a predefined assembly to use.

docker.assembly.exportBaseDir

If true export base directory

docker.assembly.ignorePermissions

If set to true existing file permissions are ignored when creating the assembly archive. Deprecated, use a permission mode of ignore instead.

docker.assembly.permissions

can be ignore to use the permission as found on files regardless on any assembly configuration, keep to respect the assembly provided permissions, exec for setting the executable bit on all files (required for Windows when using an assembly mode dir) or auto to let the plugin select exec on Windows and keep on others. keep is the default value.

docker.assembly.dockerFileDir

specifies a directory containing an external Dockerfile that will be used to create the image. This is deprecated please use docker.dockerFileDir or docker.dockerFile instead.

docker.nocache

Don’t use Docker’s build cache.This can be overwritten by setting a system property docker.nocache when running Maven.

docker.bind.idx

Sets a list of paths to bind/expose in the container

docker.buildArg.VARIABLE

Set a ARG to be available during build of image. Note: this is handled separately from external configuration, and is always available. See Build Args for more details.

docker.capAdd.idx

List of kernel capabilities to add to the container

docker.capDrop.idx

List of kernel capabilities to remove from the container

docker.cleanup

Cleanup dangling (untagged) images after each build (including any containers created from them). Default is try (which wont fail the build if removing fails), other possible values are none (no cleanup) or remove (remove but fail if unsuccessful)

docker.cmd

Command to execute. This is used both when running a container and as default command when creating an image.

docker.domainname

Container domain name

docker.dns.idx

List of dns servers to use

docker.dnsSearch.idx

List of dns search domains

docker.dockerArchive

specify an archive which can be loaded with docker load. Use this as an alternative to docker.dockerFile or docker.dockerFileDir

docker.dockerFile

specifies a Dockerfile to use. This property must point to the Dockerfile itself.

docker.dockerFileDir

specifies a directory containing an external dockerfile that will be used to create the image. The dockerfile must be name Dockerfile

docker.entrypoint

Container entry point

docker.exposedPropertyKey

Property part for the exposed container properties like internal IP addresses as described in docker:start.

docker.env.VARIABLE

Sets an environment variable used in build and run. E.g. <docker.env.JAVA_OPTS>-Xmx512m</docker.env.JAVA_OPTS> sets the environment variable JAVA_OPTS. Multiple such entries can be provided. This environment is used both for building images and running containers. The value cannot be empty but can contain Maven property names which are resolved before the Dockerfile is created.

docker.envBuild.VARIABLE

Sets an environment variable used in build only. E.g. <docker.envBuild.JAVA_OPTS>-Xmx512m</docker.envBuild.JAVA_OPTS> sets the environment variable JAVA_OPTS. Multiple such entries can be provided. This environment is building images only. The value cannot be empty but can contain Maven property names which are resolved before the Dockerfile is created.

docker.envRun.VARIABLE

Sets an environment variable used in run only. E.g. <docker.envRun.JAVA_OPTS>-Xmx512m</docker.envRun.JAVA_OPTS> sets the environment variable JAVA_OPTS. Multiple such entries can be provided. This environment is used both for running containers only. The value cannot be empty but can contain Maven property names which are resolved before the Dockerfile is created.

docker.envPropertyFile

specifies the path to a property file whose properties are used as environment variables in run. The environment variables takes precedence over any other environment variables specified.

docker.extraHosts.idx

List of host:ip to add to /etc/hosts

docker.filter

Enable and set the delimiters for property replacements. By default properties in the format ${..} are replaced with Maven properties. You can switch off property replacement by setting this property to false. When using a single char like @ then this is used as a delimiter (e.g @…​@). See Filtering for more details.

docker.from

Base image for building an image. Must be set when an image is created (or fromExt)

docker.fromExt.VARIABLE

Base image for building an image (extended format), which also triggers a build of an image.

docker.healthcheck.cmd

Command to use for a healthcheck

docker.healthcheck.interval

Interval for how often to run a healthcheck (in seconds or with a given time unit)

docker.healthcheck.mode

If se to none disable a healthcheck from a base image

docker.healthcheck.retries

Number of retries for how often to retry a healthcheck until it is considered to have failed

docker.healthcheck.startPeriod

Initialization time for containers that need time to bootstrap. Probe failure during that period will not be counted towards the maximum number of retries. However, if a health check succeeds during the start period, the container is considered started and all consecutive failures will be counted towards the maximum number of retries. (in seconds or with a given time unit)

docker.healthcheck.timeout

Timeout after which a healthcheck command is considered to be failed (in seconds or with a given time unit)

defines a list of links to other containers when starting a container. idx can be any suffix which is not used except when idx is numeric it specifies the order within the list (i.e. the list contains first entries with numeric indexes sorted and the all non-numeric indexes in arbitrary order). For example <docker.links.1>db</docker.links.1> specifies a link to the image with alias 'db'.

docker.maintainer

defines the maintainer’s email as used when building an image

docker.memory

Container memory (in bytes)

docker.memorySwap

Total memory (swap + memory) -1 to disable swap

docker.name

Image name

docker.namingStrategy

Container naming (either none or alias)

docker.network.mode

Network mode to use which can be none, host, bridged, container or custom

docker.network.name

Name of the custom network when mode is custom, or for mode container the image alias name used to create the container.

docker.network.alias.idx

One or more aliase for a custom network. Only used when the network mode is custom

docker.optimise

if set to true then it will compress all the runCmds into a single RUN directive so that only one image layer is created.

docker.portPropertyFile

specifies a path to a port mapping used when starting a container.

docker.ports.idx

Sets a port mapping. For example <docker.ports.1>jolokia.ports:8080<docker.ports.1> maps the container port 8080 dynamically to a host port and assigns this host port to the Maven property ${jolokia.port}. See Port mapping for possible mapping options. When creating images images only the right most port is used for exposing the port. For providing multiple port mappings, the index should be count up.

docker.registry

Registry to use for pushing images.

docker.restartPolicy.name

Container restart policy

docker.restartPolicy.retry

Max restart retries if on-failure used

docker.run.idx

List of commands to RUN when creating the image

docker.securityOpts.idx

List of opt elements to specify kernel security options to add to the container. For example docker.securityOpt.1=seccomp=unconfined

docker.shmsize

Size of /dev/shm in bytes.

docker.tags.idx

List of tags to apply to a built image

docker.tmpfs.idx

One or more mount points for a tmpfs. Add mount options after a :

docker.ulimits.idx

Ulimits for the container. Ulimit is specified with a soft and hard limit <type>=<soft limit>[:<hard limit>]. For example docker.ulimits.1=memlock=-1:-1

docker.user

User to switch to at the end of a Dockerfile. Not to confuse with docker.username which is used for authentication when interacting with a Docker registry.

docker.volumes.idx

defines a list of volumes to expose when building an image

docker.volumesFrom.idx

defines a list of image aliases from which the volumes should be mounted of the container. The list semantics is the same as for links (see above). For examples <docker.volumesFrom.1>data</docker.volumesFrom.1> will mount all volumes exported by the data image.

docker.wait.http.url

URL to wait for during startup of a container

docker.wait.http.method

HTTP method to use for ping check

docker.wait.http.status

Status code to wait for when doing HTTP ping check

docker.wait.time

Amount of time to wait during startup of a container (in ms)

docker.wait.log

Wait for a log output to appear.

docker.wait.exec.postStart

Command to execute after the container has start up.

docker.wait.exec.preStop

Command to execute before command stops.

docker.wait.exec.breakOnError

If set to "true" then stop the build if the a postStart or preStop command failed

docker.wait.shutdown

Time in milliseconds to wait between stopping a container and removing it.

docker.wait.tcp.mode

Either mapped or direct when waiting on TCP connections

docker.wait.tcp.host

Hostname to use for a TCP wait checks

docker.wait.tcp.port.idx

List of ports to use for a TCP check.

docker.wait.kill

Time in milliseconds to wait between sending SIGTERM and SIGKILL to a container when stopping it.

docker.workdir

Container working directory where the image is build in

docker.workingDir

Current Working dir for commands to run in when running containers

Multiple property configuration handlers can be used if they
use different prefixes. As stated above the environment and ports
configuration are both used for running container and building
images. If you need a separate configuration you should use explicit
run and build configuration sections.

Combining property and XML configuration

By default the property handler will only consider properties and ignore any other image
configuration in the XML/POM file. This can be changed by adding the <mode>
configuration (since version 0.25.0), which can have one of the following values:

Table 31. Property mode

only

Only look at properties, ignore any <run> or <build> sections for this image. This is the default, and also the behavior in versions before 0.25.0.

override

Use property if set, else fall back to value found in <run> or <build> sections for this image.

fallback

Use value found in <run> or <build> sections for this image, else fall back to to property value.

skip

Effectively disable properties, same as not specifying the <external> section at all.

Activating property configuration externally

It also possible to activate property configuration by setting the property docker.imagePropertyConfiguration to a
valid property mode, without adding an <external> section. The plugin will then use any properties with default docker. prefix.
This can be useful if most of the configuration is specified in XML/POM file, but there
is need to override certain configuration values without altering the POM file (instead add this to a parent POM or
global settings.xml).

If set in parent POM, but not wanted in specific project, the property could be overriden locally with the value skip
to disabled property configuration for that particular project.
If set in settings.xml however, by Maven design, that value will always take precedence over any properties defined in
pom.xml.

For configurations with multiple images, using this property will by default produce an error. All images would then
use the same docker property prefix, resulting in multiple identical configurations.
This can be overruled by adding an explicit <external> configuration element with an explicit <prefix> to all
images (or at least all but one). Normally you’d want to use different prefix for each image, but if explicitly set
it does allow you to use the same prefix (even docker) on all images. This is useful in case you just want to share
a few properties. This only makes sense when property mode is override or fallback and image-specific configuration
are defined in the POM configuration.

For some fields it may be desired to merge values from both POM and properties. For example, in a certain run environment
we might want to inject a http_proxy environment variable, but we do not want to add this to the POM file.

This is solved using a Combine policy which can be either replace or merge. Merge is only available for
configuration of Map or List type. For scalar values such as strings and integers, it is not supported.
For Maps, both sources are merged, with the priority source taking precedence. For Lists, they are concatenated, with values
from the priority source being added first.

Combine policy is specified per configuration key/property, and the default in most cases is currently replace. The following
keys have merge as default policy:

docker.args

docker.envBuild

docker.envRun

docker.labels

docker.ports

docker.tags

This can be overridden individually for all configuration keys (of map/list type) by setting an additional property suffixed ._combine.
For example, to not merge ports, set docker.ports._combine=replace, and to enable merging of dns, set docker.dns._combine=merge.

This would build the same image as the previous example.
If instead built with mvn docker:build -Pdocker.from=console/tomcat:8.0 -Ddocker.tags.0=tc8-test it would build from that image instead, and also add that tag to the image.

If -Ddocker.labels.status=beta is added, the image would be given two labels: status=beta and software=tomcat.
If -Ddocker.labels._combine=replace is added, the image would be given one label only: status=beta.

When the plugin is executed, on a machine with the given settings.xml, the plugin will see the docker.imagePropertyConfiguration configuration and enable
the property merging feature. When building, it will inject the http_proxy build ARG, and when running, it will inject the http_proxy ENV variable.
The rest of the configuration will be sourced from the XML, unless the Maven project has any other docker.* properties defined.

Example, external activation of property configuration, two images

Using the same global ~/.m2/settings.xml file as in previous example, but with two image definitions and no extra configuration will cause
an error, saying that you cannot use property docker.imagePropertyConfiguration on projects with multiple images.

By adding an explicit external configuration directive with the same prefix in both images, this error is disabled.

The behaviour will now be same as previous example.
Note that you must explicitly state <mode>override</mode>, otherwise it will use the default only.

6.2. Docker Compose

This plugin supports also configuration via a docker-compose file, especially for running containers specified in docker-compose.yml. Docker Compose handling is available also as an external configuration provider.

The alias of the image is used as correlation key mapping to a service in the Docker Compose file

2

An <external> configuration handler needs to be used for Docker Compose support

3

The type for the external configuration provider must be set to compose

4

Additional configuration for the handler where to find the compose file

5

Extra <build>, <run> and <watch> configuration can be provided which are used as default configuration for the Docker compose service webapp (as specified with the alias)

The following options can be provided:

Table 32. Docker compose configuration

Element

Description

Default

basedir

Basedir where to find the compose file and which is also used as the current directory when examing the compose file. Any relative volume bindings will be resolved relative to this directory.

${basedir}/src/main/docker

composeFile

Name of the compose file to use

docker-compose.yml

ignoreBuild

Ignore the compose file’s build: section and use the plugin’s build configuration exclusively.

false

The Docker Compose file can contain variables as described in the Docker Compose documentation. These are substituted with Maven project properties. Please note, when the docker-compose.yml with variables is to be used with the docker-compose CLI command, that these variables must also be valid environment variables (i.e. must not contain a .).

In addition to the docker-compose.yml you can add all known options for <build> , <run> and <watch> configuration elements which are then used as defaults and are overwritten by the configuration defined in the docker-compose.yml file. The merging between the XML configuration and the information found in docker-compose.yml is correlated via the <alias> name. E.g. if the XML image configuration is aliased with webapp then its is used as a default configuration for a Docker Compose service name webapp. All other services defined in the compose file are left untouched.

extend for including other Docker Compose files is not yet implemented.

Only services are currently evaluated, there is no supported yet for volumes and networks.

7. Registry handling

Docker uses registries to store images. The registry is typically
specified as part of the name. I.e. if the first part (everything
before the first /) contains a dot (.) or colon (:) this part is
interpreted as an address (with an optionally port) of a remote
registry. This registry (or the default docker.io if no
registry is given) is used during push and pull operations. This
plugin follows the same semantics, so if an image name is specified
with a registry part, this registry is contacted. Authentication is
explained in the next section.

There are some situations however where you want to have more
flexibility for specifying a remote registry. This might be because
you do not want to hard code a registry into pom.xml but
provide it from the outside with an environment variable or a system
property.

This plugin supports various ways of specifying a registry:

If the image name contains a registry part, this registry is used
unconditionally and can not be overwritten from the outside.

If an image name doesn’t contain a registry, then by default the
default Docker registry docker.io is used for push and pull
operations. But this can be overwritten through various means:

If the <image> configuration contains a <registry> subelement
this registry is used.

Otherwise, a global configuration element <registry> is
evaluated which can be also provided as system property via
-Ddocker.registry.

Finally an environment variable DOCKER_REGISTRY is looked up for
detecting a registry.

This registry is used for pulling (i.e. for autopull the base image
when doing a docker:build) and pushing with docker:push. However,
when these two goals a are combined on the command line like in mvn
-Ddocker.registry=myregistry:5000 package docker:build docker:push
the same registry is used for both operation. For a more fine grained
control, separate registries for pull and push can be specified.

In the plugin’s configuration with the parameters <pullRegistry> and
<pushRegistry>, respectively.

With the system properties docker.pull.registry and
docker.push.registry, respectively.

There is some special behaviour when using an externally provided
registry like described above:

When pulling, the image pulled will be also tagged with a repository
name without registry. The reasoning behind this is that this
image then can be referenced also by the configuration when the
registry is not specified anymore explicitly.

When pushing a local image, temporarily a tag including the
registry is added and removed after the push. This is required
because Docker can only push registry-named images.

8. Authentication

When pulling (via the autoPull mode of docker:start) or pushing image, it
might be necessary to authenticate against a Docker registry.

There are five different locations searched for credentials. In order, these are:

Providing system properties docker.username and docker.password from the outside.

Using a <authConfig> section in the plugin configuration with <username> and <password> elements.

Using OpenShift configuration in ~/.config/kube

Using a <server> configuration in ~/.m2/settings.xml

Login into a registry with docker login (credentials in a credential helper or in ~/.docker/config.json)

Using the username and password directly in the pom.xml is not
recommended since this is widely visible. This is easiest and
transparent way, though. Using an <authConfig> is straight forward:

The server id must specify the registry to push to/pull from, which by
default is central index docker.io (or index.docker.io / registry.hub.docker.com as fallbacks).
Here you should add your docker.io account for your repositories. If you have multiple accounts
for the same registry, the second user can be specified as part of the ID. In the example above, if you
have a second account 'fabric8io' then use an <id>docker.io/fabric8io</id> for this second entry. I.e. add the
username with a slash to the id name. The default without username is only taken if no server entry with
a username appended id is chosen.

The most secure way is to rely on docker’s credential store or credential helper and read confidential information
from an external credentials store, such as the native keychain of the operating system. Follow the instruction on
the docker login documentation.

As a final fallback, this plugin consults ~/.docker/config.json and reads credentials stored directly within this
file. This unsafe behavior happened when connecting to a registry with the command docker login from the command line
with older versions of docker (pre 1.13.0) or when docker is not configured to use a
credential store.

8.1. Pull vs. Push Authentication

The credentials lookup described above is valid for both push and
pull operations. In order to narrow things down, credentials can be
provided for pull or push operations alone:

In an <authConfig> section a sub-section <pull> and/or <push>
can be added. In the example below the credentials provider are only
used for image push operations:

When the credentials are given on the command line as system
properties, then the properties docker.pull.username /
docker.pull.password and docker.push.username /
docker.push.password are used for pull and push operations,
respectively (when given). Either way, the standard lookup algorithm
as described in the previous section is used as fallback.

8.2. OpenShift Authentication

When working with the default registry in OpenShift, the credentials
to authenticate are the OpenShift username and access token. So, a
typical interaction with the OpenShift registry from the outside is:

Alternatively the configuration option <useOpenShiftAuth> can be
added to the <authConfig> section.

For dedicated pull and push configuration the system properties
docker.pull.useOpenShiftAuth and docker.push.useOpenShiftAuth are
available as well as the configuration option <useOpenShiftAuth> in
an <pull> or <push> section within the <authConfig>
configuration.

8.3. Password encryption

Regardless which mode you choose you can encrypt password as described
in the
Maven documentation. Assuming
that you have setup a master password in
~/.m2/security-settings.xml you can create easily encrypt
passwords:

This password then can be used in authConfig, docker.password
and/or the <server> setting configuration. However, putting an
encrypted password into authConfig in the pom.xml doesn’t make
much sense, since this password is encrypted with an individual master
password.

8.4. Extended Authentication

Some docker registries require additional steps to authenticate.
Amazon ECR requires using an IAM access key to obtain temporary docker login credentials.
The docker:push and docker:pull goals automatically execute this exchange for any registry of the form <awsAccountId>.dkr.ecr.<awsRegion>.amazonaws.com, unless the skipExtendedAuth configuration (docker.skip.extendedAuth property) is set true.

You can use any IAM access key with the necessary permissions in any of the locations mentioned above except ~/.docker/config.json.
Use the IAM Access key ID as the username and the Secret access key as the password.
In case you’re using temporary security credentials provided by the AWS Security Token Service (AWS STS), you have to provide the security token as well.
To do so, either specify the docker.authToken system property or provide an <auth> element alongside username & password in the authConfig.

9. Implicit properties

There are some implicit configurations in docker maven plugin that are not so straightforward. These are simply workarouds to get docker-maven-plugin’s flow right; just to overcome limitations of Maven and other things. Some of these are mentioned below:

If the only value of the env parameter is a docker-maven-plugin internal property which has been set implicitly you have to prefix the property with a single + like in +${docker.container.test.ip}. This is necessary due to some Maven limitations which simply interpolates a lone, non defined property, to an empty string which can’t then be replaced by this plugin after the initial interpolation phase.

When providing port mapping in a format like host.ip:host.port:80, you need to prefix property with a single +. In this form, the host ip of the container will be placed into a Maven property name host.ip. If docker reports that value to be 0.0.0.0, the value of docker.host.address will be substituted instead. In the event you want to use this form and have the container bind to a specific hostname/ip address, you can declare a Maven property of the same name (host.ip in this example) containing the value to use. host:port works in the same way as described above.

10. Further reading

Examples:

Examples
are below samples/ and contain example
setups which you can use as blueprints for your own projects.